In the present study, we tested the hypothesis that chronic
inflammation and oxidative/nitrosative stress induce
caveolin 1 (Cav-1) degradation, providing an underlying mechanism of endothelial cell activation/dysfunction and pulmonary
vascular remodeling in patients with
idiopathic pulmonary arterial hypertension (IPAH). We observed reduced Cav-1
protein despite increased Cav-1
messenger RNA expression and also
endothelial nitric oxide synthase (eNOS) hyperphosphorylation in human pulmonary artery endothelial cells (PAECs) from patients with IPAH. In control human lung endothelial cell cultures,
tumor necrosis factor α-induced
nitric oxide (NO) production and S-nitrosation (SNO) of Cav-1 Cys-156 were associated with Src displacement and activation, Cav-1 Tyr-14 phosphorylation, and destabilization of Cav-1 oligomers within 5 minutes that could be blocked by eNOS or Src inhibition. Prolonged stimulation (72 hours) with NO donor
DETANONOate reduced oligomerized and total Cav-1 levels by 40%-80%, similar to that observed in IPAH patient-derived PAECs. NO donor stimulation of endothelial cells for >72 hours, which was associated with sustained Src activation and Cav-1 phosphorylation, ubiquitination, and degradation, was blocked by NOS inhibitor
L-NAME, Src inhibitor PP2, and proteosomal inhibitor
MG132. Thus, chronic
inflammation, sustained eNOS and Src signaling, and Cav-1 degradation may be important causal factors in the development of IPAH by promoting PAEC dysfunction/activation via sustained oxidative/nitrosative stress.